There are dozens of medieval castle types of silent defences that can be done, spikes at head level through the fence or at the base of the fence, a mote, fire, bows and arrow, spears, snares, traps in the woods, how about removing that bridge Rick is so fond of meeting Laurie on? or hanging some of those 100's of sheets from the prison on the fence so the Zombies can't see in, remove some of the bars from the unused cells and make reinforced barriers or spikes/spears, have a daily noise maker draw them in a different direction. At minimum have a couple of people spend an hour a day just spiking them through the fence even if you only did 1 a minute that's 120 an hour, In 2 or 3 shifts your problems would be solved. Woodbury kept making their barriers bigger and bigger, surely some of those people now reside in the prison, put their @sses to work instead of laying up in the prison cells because that's all they seem to do. The only ones I ever seeing working the field is Rick and Carl.